Improving Efficiency and Stability of Anammox through Sequentially Coupling Nitritation and Denitritation in a Single-Stage Bioreactor

Abstract

This study developed an innovative process for the treatment of low-ammonium wastewater in a single-stage bioreactor over 250 days. Partial nitritation-anammox and partial denitritation-anammox (PN/A-PDN/A) processes were combined under aerobic/anoxic operation, and a high nitrogen removal efficiency (94.6%) was obtained at a nitrogen removal rate of 0.54 kg N m–3 d–1 and a chemical oxygen demand to total inorganic nitrogen (COD/TIN) ratio of 0.28. Mass balance analysis identified anammox as the dominant nitrogen removal pathway, achieving 88.3% nitrogen loss. The abundance of anammox bacteria and their bioactivity rapidly increased and were effectively maintained, as indicated by qPCR and bioactivity tests. The PN/A-PDN/A process provided two pathways of nitrite production for anammox, which favored the enrichment of anammox bacteria and stable processing. In addition, the enrichment of anammox bacteria was promoted by selective floc discharge since anammox bacteria are mainly located in granules (relative abundance of 29.64 ± 7.89%). Competitive organisms (including heterotrophic bacteria and nitrite oxidizing bacteria), enriched in flocs, were washed out. Overall, these findings confirmed anammox, sequentially combined with PN and PDN via aerobic/anoxic strategy, as a promising alternative for mainstream anammox.

An Innovative Process for Mature Landfill Leachate and Waste Activated Sludge Simultaneous Treatment Based on Partial Nitrification, In Situ Fermentation, and Anammox (PNFA)

“…This was most notable for effluent NO 2 – -N, which increased from 16.9 mg/L to 51.4 mg/L, and the relatively high concentration of NO 3 – -N (12.2 mg/L). Anammox is a strictly anaerobic bioprocess that reduces nitrite to N 2 directly, with ammonia as an electron donor. , Due to the lack/absence of superoxide catalase or dismutase, Anammox species are poisoned by superoxide (O 2 ) or hydrogen peroxide (H 2 O 2 ) . To maintain a relatively anaerobic environment for Anammox, previous studies have employed biofilms and granule forms in some reactor configurations to protect Anammox from oxygen diffusion poisoning .…”

“…Anammox is a strictly anaerobic bioprocess that reduces nitrite to N 2 directly, with ammonia as an electron donor. , Due to the lack/absence of superoxide catalase or dismutase, Anammox species are poisoned by superoxide (O 2 ) or hydrogen peroxide (H 2 O 2 ) . To maintain a relatively anaerobic environment for Anammox, previous studies have employed biofilms and granule forms in some reactor configurations to protect Anammox from oxygen diffusion poisoning . In phase I, continuous aeration inhibited Anammox activity and led to NOB outcompeting Anammox as its abundance decreased from 3.7 × 10 10 to 2.3 × 10 10 copies/g dry sludge (Figure C).…”

“…22 To maintain a relatively anaerobic environment for Anammox, previous studies have employed biofilms and granule forms in some reactor configurations to protect Anammox from oxygen diffusion poisoning. 21 In phase I, continuous aeration inhibited Anammox activity and led to NOB outcompeting Anammox as its abundance decreased from 3.7 × 10 10 to 2.3 × 10 10 copies/g dry sludge (Figure 3C). As such, the Anammox nitrogen removal contribution decreased in a continual manner and stabilized at 44.3%.…”

Highly Enriched Anammox Bacteria with a Novel Granulation Model Regulated by Epistylis spp. in Domestic Wastewater Treatment

“…Anammox processes play a prominent role in the global nitrogen cycle, accounting for over 50% of nitrogen loss in marine systems and up to 35% of nitrogen loss in freshwater systems. − Recently, extensive attention has been focused on the anammox process in the field of biological wastewater treatment. , It converts ammonia and nitrite into nitrogen gas directly without oxygen or organic carbon consumption, thus providing an energy-saving and high-efficiency alternative for nitrogen removal from wastewater. , As for mainstream wastewater treatment, however, the efficient enrichment and retention of the slow-growing anammox bacteria (AnAOB) remain a worldwide challenge, and they have not been widely applied at present. Moreover, AnAOB with a long generation time are sensitive to the fluctuation of environmental conditions and influent quality. , In practice, especially in the activated sludge system treating domestic wastewater, the complex and diverse microbial communities compete for substrates with AnAOB, and fast-growing heterotrophic bacteria can outcompete and competitively exclude AnAOB …”

Nitrification Process in a Nuclear Wastewater with High Load of Nitrogen, Uranium and Organic Matter under ORP Controlled

“…The last innovative technologies [23,24] are System for High-Activity Ammonium Removal Over Nitrite [SHARON), Anaerobic Ammonium Oxidation (ANAMMOX) [25,26], Complete autotrophic Nitrogen Removal Over Nitrite (CANON) [27,28] and Simultaneous Nitrification-Denitrification (SND) [29]. Although this process is difficult to implement in an effluent with a high load of COD and uranium due to its toxicity levels.…”